Should I feel aggrieved?

Week 4 I had the formation 442 and Midfielder J. Williams C Palace did not feature. My #1 sub was M. Chamakh who is a forward but my #2 sub was J. Shelvey a midfielder. Yahoo changed my formation to 433 and put Chamakh in. Should it have been a straight swap Shelvey midfielder for J.Williams midfielder and stuck to the 442 that I chose???? It might be sour grapes on my part because Shelvey scored 14 while Chamakh had minus 2!!!!!!! Just curious

The substitutions are based on bench priority & legitimate formations, not like-for-like positioning. So if any player doesn't play, and his removal, along with the addition of B1 create a legitimate formation, that substitution will be made.
In your case a 4-4-2 became a 4-3-3 because Williams was removed from midfield, B1 was a striker, and the new formation is legitimate.
No shaun, you shouldn't feel aggrieved, just as I don't feel aggrieved by having RVP and Walcott (c) in my XI, with only Kolo as active bench cover! lol ... grrrr (and I sold Baines to get Walcott!)